US Patent 7222036 Method for providing PVT compensation

Delays through components of a programmable device are determined transparently to the user through the use of mimic paths. For each delay path to be measured, at least one mimic path is created that has similar components and characteristics to the actual path to be measured. A signal fed through this mimic path will experience similar delay to a signal passing through the actual path, which can be affected by temperature and voltage variations during operation. A swept clock signal can be passed to a register latching the mimic signal data, producing output that can be fed to lead/lag logic to determine a current value of the delay through the mimic path. This delay can be compared to a previous delay determination to approximate an adjustment to be made to a sampling clock used to latch the actual data into the appropriate register at the middle of the latching window.